With a 3-day return period; I love LR! I consider their used lenses a safer purchase than new, seeing as they have much more sophisticated equipment and methods for testing the quality of lenses. They keep a huge database full of data on each model of lens; any lens that doesn't perform up to par gets repaired/returned.

So do their numeric ratings on used individual lenses reflect the units' cosmetic and mechanical condition, or its optical performance or a combination of both?

Primarily cosmetic/mechanical. However if you click on a specific item, it has a some imaging (optical) metrics. Some lenses have higher resolution than others even though they are the same cosmetic condition (overall numeric rating as well) and go for the same price.

yeah because if you interested in a 1400 euro lens you could just buy the better 11000 euro lens.

i guess a ton of potential 100-400mm buyer will just buy the 200-400mm instead...

Actually, it would be the other way around. If the new 100-400L II zoom is upgraded in IQ significantly (considering it is already a good performer) you are easiliy in the zone of other primes in the focal length range...and the 200-400 zoom is not the only lens in question. Canon has kept several low priced older primes for more than a decade in this range, and while they are not sexy or new, given no new R&D or production line upgrades are needed for these as would be with a newer product, they are steady revenue generators.

People who will foot the bill for higher priced primes (may be not the 11K zoom customer, I agree) but somewhere in the midrange will pause and consider the lower priced high IQ competitor with the versatility of a zoom vs the smidge of IQ or f/stop they may garner by paying 3 or 5K more.

If the IQ and IS improve with the new 100-400L II and they will have to, at least a tad, to justify a newer version, this is not such a far fetched notion.

While I agree with the broad propositions above, there is no reason canon can't release a II version for $4K/5K just like the 70-200 variants. Why the assumption that the current lens will be phased out?

I think they can definitely improve the optics and AF speed of the existing model. I used to own a copy but found the 70-200/2.8 II + 2x III was close enough in performance to make it unnecessary to carry around two large lenses. My guess is a new version will get rid of the push-pull, improve the optics + AF, and add the newest IS. Ideally it will also function decently with a 1.4x extender on a body that can AF at F8.

I expect the price on such a lens to be about $3k. The current 100-400 and the 70-200/2.8 I both sold at nearly the same price (70-200/2.8 was a bit pricier). Therefore I wouldn't expect a new 100-400 to drastically exceed the 70-200/2.8 II.

I would certainly be in the market for such a lens and am currently holding some of my budget in hopes they will come out with something (I would jump on a 400/5.6 IS if they came out with that instead). I can't afford $11k for the 200-400, nor can I even afford the 300/2.8 II or any of the other big primes. If I had the money I would certainly buy a 600/4 II, but given my current situation a new 100-400 is a reasonable compromise. I suspect there are many other buyers like I.

I think they can definitely improve the optics and AF speed of the existing model. I used to own a copy but found the 70-200/2.8 II + 2x III was close enough in performance to make it unnecessary to carry around two large lenses.

I have the 70-200/2.8 II and its not long enough, so I was looking at the 100-400. I'll be keeping the 70-200 anyway. Your suggestion also came up as a possibility.I'm a pure amateur so a new 100-400 may be too expensive for me anyway. Do you still stick to your guns concerning the quality using the 2xIII? Certainly price, space, weight makes it very attractive as a solution.

I also have the 400/5.6 now - which I mount on a monopod to reduce the shaking - and suspect it will become the longer term replacement. This is what I will likely take on an upcoming trip to Australia. The nice thing about it is, unlike the 300/4, it takes extenders decently. The quality with a 1.4x is roughly the same as the 70-200/2.8 II + 2x III - so once Canon releases the f8 AF firmware for the 5D3 I will have a longer solution - though I plan to stay mostly at 400/5.6.

Thought I would just clarify this more. I still find that the 70-200/2.8 II + 2x III is roughly equivalent to the 100-400. The 100-400 is a tiny bit sharper, but nothing very noticeable. The AF capabilities are roughly the same.

However, at 400mm a 400/5.6 smokes both of them - both in image quality and AF quickness. The 300/4 is another possibility. Due to the F4 aperture it focuses much easier. I have had more problems at 400mm with the lens searching and have to often use the focus limiter + spot focus when animals are surrounded by branches that try to grab focus. It obviously has fewer problems when my subject is in the open.

The 300/4 has fewer problems in AF here - presumably because on the 5D3 more focus points are used with an F4 aperture lens. Another advantage of the 300/4 is it focuses much closer - so it's almost like a telephoto macro lens.

For now I have my 70-200/2.8 II and 400/5.6 both always in my bag. I removed my 2x III extender from the bag in favor of my 1.4x. At some point I may sell the 300/4 because the 70-200/2.8 II + 1.4x is very competitive with it, but I'll probably wait for some time to truly see which one I favor. I'll eventually sell the 300/4 when I have enough to buy the new 200-400/1.4x - but both the release of that lens and saving enough money for it are far away.

Native 400 in the zoom is better in my hands than the 70-200II+ 2xIII.

I find with the extender, the image clearly softens and the contrast goes down... Of course it can be bumped up in post but depends on what is acceptable to you. The images can be more than acceptable to some...

Native 400 in the zoom is better in my hands than the 70-200II+ 2xIII.

I find with the extender, the image clearly softens and the contrast goes down... Of course it can be bumped up in post but depends on what is acceptable to you. The images can be more than acceptable to some...

I guess that my main worry would be what effect it has on AF in my 5DIII. Of course the straight 400 5.6 is also an alternative. Decisions, decisions.Thanks for all your thoughts.BJD